This invention relates to dispensing apparatus. Particularly, but not exclusively it relates to dispensing apparatus for dispensing viscous materials from a container under pressure of a propellant.
Known dispensing apparatus commonly includes a valve mechanism fitted to a container which is refilled with a product, for example mastic or sealant, which is to be dispensed. Examples are disclosed in Patent document EP-B-0243393 (Rocep Lusol Holdings Limited). However, known arrangements have several disadvantages.
For example, the cost of components used in the manufacture of such known apparatus is high. This is particularly true in relation to the cans used as containers in such apparatus. Further, automatic assembly of such apparatus is complicated and costly.
Yet another disadvantage is that the product must be filled into the dispensing apparatus during manufacture of the apparatus. This involves the product manufacturer supplying the product in bulk to the apparatus manufacturer who then returns the filled apparatus to the product manufacturer for sale. This is costly and inconvenient. As a result of the foregoing, the overall costs associated with presently available dispensing apparatus are high.
Known dispensing apparatus, such as that disclosed in EP-B-0089971 (Rocep Lusol Holdings Limited), include piston arrangements which are designed to prevent propellant gas in the apparatus from coming into contact with the product to be dispensed. Commonly, these piston arrangements consist of a pair of pistons with sealant therebetween. However, known arrangements can be costly to manufacture and have the significant disadvantage that after filling of the apparatus, and during storage, the sealant expands causing the pistons to separate from one another. This problem has to be addressed by xe2x80x9cnecking inxe2x80x9d the can (ie locally reducing the diameter of the can) below the piston assembly to prevent separation. It would be desirable to have a piston arrangement which would stay together without the need for xe2x80x9cnecking inxe2x80x9d the can.
It would also be desirable to have dispensing apparatus such that a manufacturer can fill the apparatus with product himself, after the apparatus has been assembled and/or pressurised, and to have dispensing apparatus which is refillable.
According to a first aspect of the present invention there is provided dispensing apparatus for dispensing a product from a container under pressure of a propellant, said apparatus comprising a product chamber within the container and a valve adjacent to the product chamber characterised in that the valve allows product flow into and out of the product chamber.
Preferably, the product chamber is pressurised. The product chamber preferably contains a piston, situated between the propellant and the valve.
Preferably, the piston is an interlocking double piston. The interlocking sections preferably have a sealant between them. The sealant forms a substantially impenetrable barrier between the propellant and the product.
Preferably, the valve is operated by means of an actuator and a lever. The lever may be manufactured of plastics material; it may be manufactured as a single piece of plastic, for example by injection moulding.
Preferably, the actuator and the lever co-operate by means of a screw thread arrangement. Turning of the actuator relative to the lever may vary the flow rate of product out of the apparatus. Turning may be possible from a xe2x80x9clock-offxe2x80x9d position, in which the actuator is clicked home, to a fully on position. Markings may be provided to show the flow rate corresponding to predetermined positions on the lever.
Means may be provided to demonstrate to a user that the actuator is in the closed position, ie the position in which no product can flow. It is further preferred that the actuator is provided with means to limit the travel of the actuator once the fully open position is reached. Said means may also prevent the actuator from being opened too far or being completely removed from the apparatus. Said means may be a groove or substantially axial slot in the external wall of the actuator.
Preferably, the container is made substantially from tin plate or aluminium. Most preferably the container is a wall ironed tin plate can. For example, it may be an extruded tin plate can as used in the beverage industry, without a side seam.
According to a second aspect of the present invention there is provided a composite piston for use in dispensing apparatus, said composite piston comprising a first piston, a second piston and a coupling means, the coupling means movably coupling the first and second pistons to each other and permitting limited relative movement between the first and second pistons in a direction substantially parallel to the direction of movement of the composite piston.
Preferably the first and second pistons interlock in use defining a piston sealant chamber.
Preferably the piston sealant chamber is open circumferentially.
Preferably, the coupling means comprises a projection on one of the first and second pistons and a recess in the other of the first and second pistons, and the projection engages in the recess to couple the pistons to each other.
Typically, the projection is of a smaller dimension than the recess to permit movement of the projection within the recess to facilitate the limited relative movement of the first and second pistons. Preferably, the projection and the recess include mutually engageable ratchet formations which permit movement of the pistons relative to each other in one direction only. Preferably, the one direction is movement of the pistons towards each other.
Typically, the recess is a central aperture in one of the pistons and the projection is a central projection on the other piston arranged to engage the recess.
Preferably, the first piston and/or the second piston may be elastically distorted to permit a push fit engagement of the projection into the recess.
Typically, the pistons may be manufactured from a flexible material, such as plastic.
Preferably, the composite piston also includes a viscous substance which in use contacts the inside wall of a container adjacent the composite piston. The viscous substance may help to facilitate sealing of the composite piston against the inside walls of the container and/or reduce friction between the composite piston and the inside walls of the container.
Preferably the viscous substance is a sealant, such as a glycerine and starch mixture. Preferably the sealant is adapted to contact the interior surface of the container, thereby forming a seal. This seal may be an annular ring of sealant in contact with the container. This prevents propellant in the apparatus from coming into contact with product in the apparatus.
One or both of the primary and secondary portions may be provided with an aperture and/or a valve to allow gas to escape out of the sealant chamber in use. Said valve may be a check valve; it may be provided in a stem provided in the centre of the secondary portion.
Preferably the piston assembly is provided with means for accommodating expansion of the sealant, in use. This may help prevent piston separation. Said means may be thinned portions provided on the primary and/or secondary piston. Preferably, said means is a plurality of thinned pockets in the wall of the secondary piston. These pockets may balloon to accommodate sealant expansion in use.
According to a third aspect of the present invention there is provided a container for dispensing a product therefrom, the container comprising a piston according to the second aspect movably mounted within the container and an outlet through which the product is dispensed, the container walls and the composite piston defining a product chamber within the container, and movement of the composite piston within the container towards the outlet expelling product through the outlet.
Typically, the viscous material is located between the first and second pistons and may be forced into engagement with the inside wall of the container by a compression force which acts between the first and second pistons to cause the second piston to move towards the first piston.
Preferably, the composite piston also includes a wall engaging skirt which abuts against an inside wall of the container. Preferably, a wall-engaging skirt is provided on both the first and the second pistons.
Preferably, the container is a pressure pack dispenser which comprises a propellant system which pushes the piston towards the outlet. However, alternatively, the piston could be used in combination with a mechanical actuating device which pushes the composite piston towards the outlet of the container.
According to a fourth aspect of the present invention, there is provided a container for use in dispensing apparatus, said container comprising a hollow cylindrical portion and a boss portion, said cylindrical portion being open at one end for attachment of a sealing dome and having a curled in portion at the other end for engagement with a corresponding flange provided on the boss portion.
Preferably, the cylindrical portion is made substantially from tin plate or aluminium or other suitable material.